The story of Bach’s Musical Offering (Das musikalische Opfer) is well known: on a 1747 visit to Frederick II’s court at Potsdam, the king presented Bach with a theme (thema regium). Reportedly, he requested that the venerable musician improvise a six-part fugue on his offering, but Bach demurred on grounds that not all themes were well suited to six-part treatment. (He did apparently please the king and guests with other improvisations during the visit.) Just two months later, however, Bach presented the King with The Musical Offering: a collection of fugues, canons, ricercares, and a trio sonata on the thema regium. Included was the six-part composition the King had requested: Fuga (Ricercata) a 6 voci, described by one historian as “Bach’s richest piece of fugal writing.”

Composers of all stripes have, of course, been attracted to Bach’s music as a source for arrangement or a point of departure for original composition – an eminently appropriate tribute, given Bach’s own penchant for tinkering with the works of others. It’s no wonder that Webern was among them, or that he would have selected this piece in particular. He shared the baroque composer’s love of musical puzzles, palindromes, and numerological symbolism, not only for its intellectual dimension but out of a conviction that these musical structures connected earthly sound to spiritual truth. Even Webern’s turn to the system of 12-tone composition represented an acceptance of tone rows as a kind of natural law: “between the products of nature and those of art no essential difference prevails,” as he once put it.

Webern orchestrated the six-part ricercare from The Musical Offering in 1934-1935. Ricercare means “to seek,” a term well-suited to a piece that represents the exploration of an 18th-century composition through a 20th-century musical consciousness. That the result is so Webernesque makes clear that Webern’s signature style is less indebted to atonality or dissonance than it is to his techniques of Klangfarben-melodie (using tone color as a melodic element) and motive separation.

The piece opens with two and a half measures of solo trombone; overlapping sonorities of French horn and trumpet complete the statement of the theme.

As Bach’s counterpoint becomes denser, Webern introduces the entire ensemble of fifteen, mostly solo, instruments. In spite of his pointillistic allocation of Bach’s lines among the fifteen voices, Webern was clear that motive separation did not mean dissolution: “The theme throughout must not appear disintegrated. My orchestration tries (here I am speaking of the whole work) merely to reveal the motivic coherence.”

Indeed, Webern’s spare orchestration not only maintains Bach’s motivic coherence, but his manipulation of the widely spaced timbres creates a transparent, crystalline texture that is a revelation in itself: it both highlights the existing relationships between melodic line and timbre and allows new ones to emerge. So too does Webern’s judicious use of instructions adding interpretive details of phrasing, articulation, dynamics, and rubato to bring out the relationship between small- and large-scale musical structures. In sum, a work that is at once familiar and unfamiliar, an imaginative bridge across two centuries.

— A musicologist specializing in 20th-century American music, Susan Keyis a frequent contributor to the Philharmonic’s program book.